(a) The Field of the invention
This invention refers in general to a thermostable flameproofing agent for polyester compositions suitable for the production of formed bodies, in particular fibers, to a process for its preparation and to a technique for the production of said formed bodies having properties of resistance to the propagation of the flame.
More particularly this invention refers to a product suitable for use as thermostable flameproofing agent for bodies formed from polyester compositions, essentially on a polyethyleneterephathalate and/or polybutyleneterephthalate basis.
(B) The prior art
Methods for the production of formed bodies, in particular fibres, from copolyesters resistant to the propagation of the flame are known in the art.
Two general methods are known to confer to said formed bodies properties of resistance to the propagation of the flame: specifically one of them involves incorporating flameproofing additives in the polyester compositions before the extrusion, while the other involves applying said additives as finishes to the already formed bodies.
With regard to the textile industry, it is much preferable to make fibers from spinnable copolyester compositions which contain flameproofing additives and/or combinations thereof than to apply flameproofing finishes to the fibers and the textile articles.
This latter method is disadvantageous because the flameproofing finish has a short life and is progressively removed in the course of the use and the washings of the textile article, as is well known in the art. Therefore the more recent art is oriented to the preparation of polyester compositions already comprising flameproofing agents, for the production of flameproofed formed bodies, in particular textile articles.